Inner Diameter Adapter for Cardboard Spools, included for Fugacity (55.6mm inner diameter), Yousu (53.4mm ID) and Polymaker (55.1mm ID) spools, but you can customize the model for your spool by editing the fusion 360 models and adjusting the inner diameter. When creating the adapter, err on the side of oversizing the inner diameter (by 0.1mm or 0.2mm) the adapter so it "bites" on the cardboard and won't move when on a spool holder.